JPS63303529A - System for supervising radio line quality - Google Patents

Abstract

PURPOSE:To execute the accurate supervision of a transmission quality and the accurate discrimination of the deterioration cause at the time of the quality deterioration by supervising the number of transmission line code rules, a receiving electric field level, the same channel interference ratio, and the state of frame synchronizing step-out of a data signal. CONSTITUTION:After a data signal is separated by a low pass filter 17 from the output of a receiver 13, a transmission line code and an error correcting block code are decoded by decoders 19 and 21. Based on a pulse 29 to show the transmission line code rule destruction occurrence from the decoder 19, the number of transmission line code rule destructions is obtained by a counter 31, and based on an envelope output 34 of the receiver 13, a receiving electric field level is obtained by a level measuring circuit 35 and the same channel interference ratio is obtained by a same channel interference ratio measuring circuit 39. Based on the deciding result concerning whether or not the frame synchronizing step-out state obtained by a frame synchronizing protecting circuit 24 is obtained, the number of the above-mentioned rule destructions, a receiving level and an interference ratio, the supervision of the transmission quality and the discrimination of the deterioration cause at the time of the quality deterioration are executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical field to which the invention pertains The present invention relates to a system for highly accurately monitoring radio channel quality in a mobile communication system that transmits voice signals.

(2) Prior art and its problems In mobile communication systems where voice transmission quality fluctuates due to fading, it is necessary to detect deterioration in voice transmission quality and perform radio line control such as channel switching.

Conventionally, in mobile communication systems, a method of detecting the median value of the received wave level of a communication channel has been adopted as a method for monitoring the transmission quality of a voice signal after a communication channel is set. However, the accuracy of the envelope detector, which outputs a voltage proportional to the received wave level, becomes extremely poor at low levels that degrade the transmission quality of audio signals, making it difficult to monitor and control wireless lines with high precision. There were drawbacks.

As a method to improve this drawback, Japanese Patent Application No. 57-21702
As shown in No. 4, deterioration in voice transmission quality is detected by combining quality monitoring of data signals transmitted simultaneously with voice during a call and conventional central detection of received wave levels. A method has been proposed to determine whether the cause is level deterioration or interference. However, in the method shown in Japanese Patent Application No. 57-217024, the method for detecting deterioration in audio transmission quality involves error-correcting coding of a data signal that is transmitted simultaneously with audio, and monitoring the syndrome sequence obtained in the decoding process. method is limited.

For this reason, if error correction coding is not performed, this method not only cannot be used, but also transmission path coding (
For example, the redundancy provided in split-phase codes, bipolar codes, etc.) is not used at all.Normally, mobile radio transmission systems have the disadvantage that the characteristics of the transmission path (for example, in the case of FM transmission systems, low-frequency cut-off characteristics) In order to comply with the above-mentioned requirements, transmission line encoding of data signals is often performed, and for this purpose, redundancy is provided on a bit-by-bit basis.

Japanese Patent Application No. 57-217024 makes no mention of using this redundancy on the receiving side.

On the other hand, when co-channel interference occurs, the envelope of the received wave exhibits a beat phenomenon, but when the lower audio band (0 to 300H2) is used as the transmission band for data signals transmitted simultaneously with audio, this beat Since the frequency component is significantly different from the frequency component of received wave level fluctuation due to fading, it is possible to separate both signals in terms of frequency. Patent Application No. 18102/1983 focused on this,
A method has been proposed for determining the desired wave to interference wave power ratio (hereinafter abbreviated as D/U) when co-frequency interference occurs by measuring the power of the beat component. However, this method has the drawback that the range of D/U that can be determined with high accuracy is extremely narrow. Figure 1 shows an example of the characteristics of D/U measurement according to the method of Japanese Patent Application No. 18102/1983 when a data signal to 100b is superimposed on the lower band of audio. U, @1 axis is the measured value, and the Doppler frequency f of fading is 40Hz. I know that it will happen.

In this way, the conventional method of monitoring voice transmission quality and determining its cause separately does not allow accurate monitoring and determining its cause, making effective wireless line control difficult. The drawback was that it could not be done.

(3) Purpose of the Invention The purpose of the present invention is to eliminate these drawbacks in the prior art, and to accurately monitor audio transmission quality and, when deterioration in audio transmission quality is detected, to accurately identify the cause of the deterioration ( It is an object of the present invention to provide a radio channel quality monitoring method that enables effective radio channel monitoring through discrimination.

(4) Structure of the invention (4-1) Differences between the characteristics of the invention and the conventional technology The present invention has the following features:
By measuring the number of violations of the transmission line code rules of the data signal transmitted using the lower band of the audio signal in a predetermined time interval, the audio transmission quality can be accurately monitored (monitored), and this can be combined with reception level measurement and co-channel interference ratio. The main feature is the combined use of measurement and data signal frame synchronization protection state detection.

The conventional technology is that (i) redundancy provided by channel coding and detection of frame synchronization protection status are used to monitor voice transmission quality, and (ii) reception level measurement and co-channel interference ratio measurement results are used. The difference is that the method does not control the radio channel solely by the method, but uses the results of reception level measurement and co-channel interference ratio measurement to determine the cause when deterioration in voice transmission quality is detected.

(4-2) Example Examples of the present invention will be described in detail below.

FIG. 2 is a diagram showing an embodiment of the present invention, and FIG.
) is the device configuration on the transmitting side, and FIG. 2(B) is the device configuration on the receiving side.

In FIG. 2(A), 1 is a control data input, and 2 is a frame signal encoder which configures data into a frame signal.

3 is a frame signal encoder output, and 4 is a transmission line code encoder, which further encodes the data 3 encoded into the frame signal into a transmission line code. 5 is the encoder output of the transmission line code, and 6 is a low cutoff filter (LEF) that removes leakage components of control data into the voice band. 7 is the output of the low-cut filter 6, 8 is the audio signal input, 9 is an analog adder that synthesizes the output of the LEF 6 and the audio signal 8, and 10 is the modulated carrier wave that is modulated by the output of the analog adder 9. A transmitter (TX) that transmits waves, 11 is a transmitting antenna.

In addition, in FIG. 2 (B,), 12 is a receiving antenna;
13 is a receiver that receives the modulated wave transmitted from the transmitting side, 14 is the demodulated receiver output, 15 is a band pass filter (BPF) for separating the audio signal, 16 is the audio signal output, and 17 is the audio signal output. A band pass filter (LPF) for separating control data, 18 is a low pass filter (LPF)
) output, 19 is the transmission line code decoder, 20 is the transmission line code decoder output, 21 is the frame signal decoder, 22 is the frame signal decoder output, and the data input from the transmitting side is output. . 23 is a timing pulse output indicating that a frame signal has been received, and one pulse is output every time one frame signal can be received. 24
is a frame synchronization protection circuit, and the timing pulse 23
, and determine whether it is in a synchronous protected state or an unprotected state. Reference numeral 25 indicates the determination result of the synchronization protected state or non-protected state, which corresponds to 0" and "l", respectively. Reference numeral 26 indicates the start of frame signal reception under the synchronization protection state by the transmission path code decoding circuit 19 and the frame signal. A reception start pulse output instructing the decoding circuit 21, 27 is a frame signal start pattern detection circuit, 28 is a pulse output output when the start pattern is detected, and is sent to the transmission line code decoder 19 and the frame signal decoder 21. 29 is a pulse output indicating that a rule break of the transmission line code has occurred, and one pulse is output every time the rule break occurs during decoding of the transmission line code. 30 is a rule break. a regular breaking pulse counter that calculates the number of pulses 29 in a predetermined time interval;
31 is the number of rule-breaking pulses, and 32 is a comparison circuit that determines whether the number of rule-breaking pulses exceeds a predetermined value. 3
3 is a determination result that the number of pulses is greater than or equal to a predetermined value. 34 is a received wave envelope output, which is obtained from a received envelope detection output provided in the receiver. Reference numeral 35 denotes a level measuring circuit for determining the received electric field level of the received modulated wave in a predetermined time interval, 36 the received electric field level value, and 37 a comparison circuit that determines whether the received electric field level value is less than a predetermined value. 38 is a determination result that the received electric field level is below a predetermined value. 39 is a co-channel interference ratio measurement circuit, patent application 1983-
It is determined whether the D/lJ measured by the co-channel interference ratio measurement method shown in No. 18102 is greater than or equal to a predetermined value, and if the measured value is less than or equal to the predetermined value, 1";
If not, output "0". 40 is an interference detection output. Reference numeral 41 indicates a time rate measurement circuit for determining the time rate of a predetermined time interval of the interference detection output, 42 indicates a time rate value of the predetermined time interval of the interference detection output, and 43 indicates whether the time rate of the predetermined time interval of the interference detection output exceeds a predetermined value. a comparison circuit for determining 44
is the determination result as to whether the predetermined time interval time rate of the interference detection output is equal to or greater than the predetermined value. Reference numeral 45 denotes a logic circuit that operates when the signal 25 indicating the synchronization protection state becomes an unprotected state or when the judgment result 33 that the number of pulses breaking the transmission line code rule is equal to or greater than a predetermined value is equal to or greater than a predetermined value. , it is determined whether these causes are due to the received electric field level being below a predetermined value or due to the time rate of the co-channel interference detection output being above a predetermined value. 46 is a logic circuit 45
This is the judgment output.

Next, specific operations of each component in this embodiment will be described. In FIG. 3, (A) shows the signal configuration of the control data input 1, (B) the encoder output 3 of the frame signal, and (C) the signal configuration of the encoder output 5 of the transmission line code. Also, C0
NT indicates control data, ST indicates a start pattern necessary for frame synchronization of control data, and control data C
When 0NT is encoded into a frame signal, it is often encoded into a block code using an error correction code, and in that case, it is encoded into a code in which a check code is added to control data C0NT. CIIK indicates a check code. Therefore, the frame signal is composed of the start pattern ST, control data C0NT and check code CHK, and the hit rate increases by the addition of the start pattern and check code. As mentioned above, transmission channel coding is performed to adapt the code to the characteristics of the transmission channel. FIG. 3 shows an example in which a split phase code is used as the transmission line code. The split phase code is a code that makes "1" correspond to "01" and "0" to "10", and the DC balance is perfectly maintained within one bit, making it easy to extract the clock component on the receiving side. In this case, in order to prevent the same pattern from occurring in the control data C0NT and check code CHK, the start pattern part has the following advantages:
Transmission path encoding is often not performed.

On the receiving side, decoding is performed in the reverse order to that described above. That is, after the data signal is separated from the audio signal by the low-pass filter 17, the transmission path code is decoded by the transmission path code decoder 19, and then the frame signal decoder 21 decodes the transmission path code.
Decode the error correction block code. The start pattern detection circuit 27 constantly detects the start signal pattern ST from the received bit sequence, and when the start pattern ST is detected, the start timing of decoding of the subsequent frame signal is determined by the frame signal decoder 21. and outputs pulses to be applied to the transmission path code decoder 19. Transmission path code decoder 19 and frame signal decoder 2
1, the decoding start timing is determined by the output of the frame synchronization protection circuit 24 and the start pattern detection circuit 27, which will be described later.
It is obtained from the detection pulse 28 which is the output of .

In the frame synchronization protection circuit 24, at the timing when the timing pulse 23 indicating that the frame signal has been received is input, a determination result 25 indicating that the synchronization protection state is the non-protection state is generated.
is placed in a synchronization protection state, and a timer for one frame time of the frame signal is started. When the timer times up, one pulse is output as the reception start pulse 26. Normally, the above operation continues, but if an out-of-synchronization condition is detected, the device enters a non-protected state and stops the operation. The out-of-synchronization detection condition is detected when the timing pulse 23 indicating that a frame signal has been successfully received is not input a predetermined number of times in succession. In the transmission line code decoder 19 and the frame signal decoder 21, when the signal 25 indicating the synchronization state is in the synchronization protection state, the frame signal decoding operation is performed using the reception start pulse 26 from the frame synchronization protection circuit 24 as a trigger pulse. is started, and when it is in the unprotected state, the frame signal decoding operation is started using the start pattern detection pulse 28 from the start pattern detection circuit 27 as a trigger pulse.

Frame synchronization protection as described above means that when frame signals are transmitted continuously as shown in Figure 3, once a frame signal is received normally, the beginning of the frame signal will be synchronized at a fixed timing. Since there are parts
If this timing is reproduced on the receiving side, the decoding operation for one frame can be started without detecting the start pattern ST for each frame. Therefore, even if the reception probability of the start pattern ST is low, it is possible to avoid a phenomenon in which the frame signal cannot be received because the start pattern ST cannot be received.

On the other hand, when the asynchronous protection state is entered, the detection of the start pattern ST is used as a trigger pulse to start the decoding operation, thereby starting the operation for transitioning to the synchronous protection state again. What should be noted here is that when an out-of-sync condition is detected in the synchronization protection state, this corresponds to a deterioration in the transmission path condition due to a drop in the received electric field level or the occurrence of co-channel interference. It also copes with deterioration in the transmission quality of transmitted audio signals.

As described above, the transmission line code decoder 19 decodes the transmission line code, and at this time it is possible to detect bits in which the rules of the transmission line code have been broken. In the case of the above-mentioned split phase code, since "0" corresponds to "1o" and "1" corresponds to "01", the latter half bits correspond to the original information. Therefore, in the transmission line code decoder 19, the original information can be decoded from the latter half bits, but in this case, if the first half bits and the latter half bits have the same decoding result, the split phase code The rules have been broken. Transmission path code rule breaking detection pulse output 29
In this case, one pulse is output every time a bit in which such a rule violation of the transmission path code occurs is detected, and the counting circuit 30 calculates the number of pulses in a predetermined time and outputs the value.

FIG. 4 shows a method for determining the number of pulses. (a) is a pulse train for detecting rule breaking of the transmission path code, and the number of pulses within the time interval T of this pulse train is
The results obtained at the timings of . . . , ■, . . . are shown above the corresponding arrows. What should be noted here is that breaking the rules of the transmission path code is caused by noise generated on the transmission path, so if the number of pulses is large, it corresponds to the deterioration of the transmission quality in that time interval. It also deals with deterioration in audio transmission quality due to electric field level deterioration or co-channel interference.

As mentioned above, when voice transmission quality deteriorates due to deterioration of the received electric field level or occurrence of co-channel interference, this may occur due to loss of synchronization protection of control data transmitted simultaneously with voice or an increase in the number of rules broken in the transmission path code. can be detected.

Therefore, by using the measurement results of the received electric field level in a predetermined time period together with the results of the co-channel interference ratio measurement according to Japanese Patent Application No. 58-18102, it is possible to determine the cause of the deterioration of the audio transmission quality. Circuit 35 for determining the received electric field level
measures the received electric field level in a predetermined time interval.

The received electric field level value that is the output is compared with a predetermined value by the comparator circuit 37, and if it is less than the predetermined value, the judgment result output is set to "1". The co-channel interference ratio obtained has practical accuracy only within a limited D/U range. Figure 1 shows the D/U measured by the co-channel interference ratio measurement circuit and the This is an example of the true D/U relationship when modulating with audio at the maximum Doppler frequency of 4011z.The practical actual D/U range is 5≦D/
Limited to U≦15 (dB). Therefore, each time the measurement is completed, it is checked whether the D/U measurement result in the measurement time interval is above or below a predetermined value (the smaller the D/U value, the worse the interference condition is). By determining the time rate of this determination result in a predetermined time interval, the number of measurements in which it was determined that the D/U has deteriorated in the corresponding time interval is determined. The method for determining the time rate is the same as the method shown in FIG. The predetermined time interval time rate value 42 of the interference detection output is compared with a predetermined value by the comparison circuit 43, and if it exceeds the predetermined value, the judgment output is set to "1".

Next, the operation of the logic circuit 45 will be explained. The logic circuit 45 determines whether the synchronization protected state or non-protected state is determined (25.degree.) and the determination result (33.) that the number of transmission path code breaks is equal to or greater than a predetermined value. When the determination result 38 that the received electric field level is below a predetermined value and the determination result 44 as to whether the mobile phase value in the predetermined time interval of the interference detection method is above the predetermined value are input, and deterioration in audio transmission quality is detected. Next, it is determined whether the cause is a decrease in the received electric field level or co-channel interference, and the result is output.

FIG. 5 shows an example of the configuration of the logic circuit 45. In FIG. 5, 47 is an OR circuit, 48 is an inverter, and 49 is an AND circuit.
Circuit, L, and v are the results of determination that the deterioration of audio transmission quality is due to a decrease in reception level, and when it is determined that the deterioration in audio transmission quality is due to level deterioration, it becomes "1".

■□ is the result of determination that the deterioration in audio transmission quality is due to co-channel interference; when it is determined that the deterioration in audio transmission quality is due to co-channel interference, it becomes "l".

FIG. 6 is a time chart showing an example of the operation of the logic circuit shown in FIG. In FIG. 6, SO3 is a signal indicating the determination result of whether the synchronization protection state or non-protection state is present, S33 is a signal indicating the determination result that the number of code breaks in the transmission path is greater than or equal to a predetermined value, and 5311 is a signal indicating that the received electric field level is a predetermined value. S, 4 is a signal indicating the determination result that the time rate value of the predetermined time interval of the interference detection output is equal to or greater than the predetermined value, and S L 11 v is the signal indicating the determination result that the time rate value of the interference detection output in the predetermined time interval is greater than or equal to the predetermined value. The signals S and Rt indicating the determination result that the deterioration is due to a decrease in the reception level are signals indicating the determination result that the deterioration in voice transmission quality is due to co-channel interference. The case of FIG. 6 shows that voice transmission quality is degraded due to co-channel interference. In the logic circuit shown in FIG. 5, when (deterioration of audio transmission quality) and (detection of level deterioration) and (non-detection of co-channel interference),
It is determined that the deterioration in audio transmission quality is due to level deterioration, and when (deterioration in audio transmission quality) and (co-channel interference detection), it is determined that the deterioration in audio transmission quality is due to co-channel interference.

(5) As described in detail, the present invention monitors audio transmission quality by constantly monitoring the frame synchronization protection state of control data transmitted simultaneously with audio and format destruction of transmission path code on the receiving side, When the deterioration is detected, the reception electric field level and the state of co-channel interference, which are monitored in parallel, are read to determine which cause is causing the deterioration in audio transmission quality. Conventional voice transmission quality monitoring methods independently detect a drop in the received electric field level and co-channel interference, but electric field level measurement circuits have extremely poor accuracy when the electric field level is low, while detecting co-channel interference. Ratio measurement circuits have a very limited practical range of R/U. Therefore, even though there is no actual deterioration in audio transmission quality, there is a risk that a drop in the received electric field level or the occurrence of co-channel interference may be detected, leading to malfunctions in radio line control such as channel switching. Ta. In the present invention, since deterioration in voice transmission quality is detected with high precision and the cause thereof is determined, such drawbacks can be eliminated. Therefore, highly accurate voice transmission quality monitoring and effective wireless line control are possible. It has the advantage of being possible.

[Brief explanation of the drawing]

Fig. 1 shows an example of the characteristics of the co-channel interference ratio measuring method shown in Japanese Patent Application No. 18102/1982, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 shows a communication system to which the present invention is applied. FIG. 4 is a diagram showing the signal configuration on the transmitting side, FIG. 4 is a time chart showing the method of determining the number of pulses in the present invention, and FIG.
The figure is a block diagram showing an example of a logic circuit used in the present invention.
FIG. 6 is a time chart showing an example of the operation of the logic circuit shown in FIG. 1... Control data input, 2... Frame signal encoder, 3... Frame signal encoder output, 4... Transmission line code encoder, 5... Transmission line code encoder Output, 6
...Low frequency cutoff filter, 7...Low frequency cutoff filter output, 8...Audio signal input, 9...Analog adder,
10... Transmitter, 11... Transmitting antenna, 12...
- Receiving antenna, 13...Receiver, 14...Receiver output, 15...Band pass filter for audio signal separation, 1
6...Audio signal output, I7...Low pass filter for control data separation, 18...Low pass filter output, 1
9... Transmission line code decoder, 20... Transmission line code decoder output, 21... Frame signal decoder, 22.
... Frame signal decoder output, 23... Timing pulse output indicating reception of frame signal, 24... Frame synchronization protection circuit, 25... Judgment result of synchronization protection state or non-protection state, 26. ...Reception start pulse output, 27
... Start pattern detection circuit, 28... Start pattern detection pulse output, 29... Transmission line code rule breaking pulse output, 30... Transmission line code rule breaking pulse counting circuit, 31... Rule breaking Number of pulses, 32... Comparison circuit for the number of rule-breaking pulses, 33... Judgment result that the number of rule-breaking pulses is greater than or equal to a predetermined value, 34... Received pulse envelope output, 35... Predetermined time Circuit for calculating the received electric field level of the section, 36... Received electric field level value, 3
7... Comparison circuit for received electric field level, 38... Judgment result that the received electric field level is below a predetermined value, 39...
- Co-channel interference detection circuit, 40... interference detection output, 41... circuit for calculating the time rate of interference detection output, 42
... Time rate value of interference detection output, 43... Comparison circuit for request rate value of interference detection output, 44... Judgment result that time rate value of interference detection output is equal to or greater than a predetermined value, 45. ...Logic circuit, 46...Output of logic circuit, 47...OR circuit, 48...Inverter, 49...AND circuit, C
0NT...Control data, ST...Start pattern, CHK...Check code, T...Time section,'
l1ls...Signal indicating the determination result whether the synchronization protected state or non-protection state, S33...Signal indicating the determination result that the number of transmission path code breaks is greater than or equal to a predetermined value, sia...Receiving electric field level A signal indicating a determination result that the moving average value is less than or equal to a predetermined value, S44...A signal indicating a determination result that the time rate value of a predetermined time interval of the interference detection output is greater than or equal to a predetermined value, S Lev... - A signal indicating the determination result that the deterioration of audio transmission quality is due to a decrease in reception level,
5lnt4...Signal indicating the determination result that the deterioration of audio transmission quality is due to same channel interference, L e
v...Determination result that the deterioration of audio transmission quality is due to a decrease in reception level, 111. ...Determination result that the deterioration in audio transmission quality is due to co-channel interference.

Claims (1)

[Claims] (1) In a mobile radio communication system that simultaneously transmits communication signals and data on the same channel, the transmitting side has means for configuring the data into a frame signal, and converts the frame signal into a transmission path code suitable for the characteristics of the transmission path. and a means for modulating a carrier wave with the transmission path code and the speech signal to transmit a modulated wave; A circuit for separating, a means for decoding the transmission line code of the separated data and a frame signal, a means for detecting the number of rule breaks of the transmission line code in the decoded frame, and a demodulated frame. means for detecting that the signal has been received; means for detecting an out-of-synchronization state in which the frame signal cannot be received at a predetermined timing consecutively a predetermined number of times; and measuring the received electric field level of the modulated wave. means for measuring a co-channel interference ratio from the beat component power of the modulated wave; and means for measuring a percentage of time during which the co-channel interference ratio deteriorates below a predetermined value; Detection of deterioration in the transmission quality of the audio signal using a signal indicating that the number of code rule breakdowns, the received electric field level, and the time rate of deterioration of the co-channel interference ratio have respectively deteriorated from predetermined values, and a signal indicating the out-of-synchronization state. A wireless line quality monitoring method configured to be able to determine the cause of deterioration.